Effect of osmotic stress on the growth of epicotyls of Cicer arietinum in relation to changes in the autolytic process and glycanhydrolytic cell wall enzymes

Simulation of drought by polyethylene glycol (PEG) inhibited elongation of epicotyls of Cicer arietinum L. cv. Castellana but had no effect on growth capacity since growth was restored once the inhibitory condition had been removed. The amount of proteins in the cell wall was correlated with the elongation of the epicotyls and decreased when elongation was inhibited. PEG-induced inhibition of elongation had different effects on the various glycanhydrolytic cell wall enzymes. Only α-galactosidase (EC 3. 2. 1. 22) seemed related to the lack of elongation, increasing its activity when elongation was inhibited. The β-galactosidase (EC 3. 2. 1. 23) and β-glucosidase (EC 3. 2. 1. 21) studied did not show changes in their specific activities during the inhibition of elongation. β-Galactosidase is responsible for the autolytic process in Cicer arietinum . This enzyme hydrolyzes specified linkages in the cell wall, releasing sugar constituents. Our present results show that β-galactosidase is not directly related with elongation because no changes could be observed during inhibition of elongation. The autolytic process is related with chemical processes taking place in the cell wall and preceding elongation of the epicotyls, i. e. the loosening process. Cell wall loosening is necessary for elongation to take place but elongation does not necessarily follow loosening if the osmotic conditions are unfavorable     

Adenylate Uptake by Proplastids from Cultured Cells of Tobacco {Nicotiana tabacum L. cv. BY2) Indicates That an Adenylate Translocator is Present in All Types of Plastid

The presence of an adenylate translocator in the envelope membranesof proplastids isolated from the cultured cells of tobacco (Nicotianatabacum L. cv. BY2) was examined by means of transport experimentsusing the silicone oil filtering centrifugation technique. Itwas observed that proplastids can import [³H]ATP, [³H]ADP, [³H]AMPand less specifically ADP-[¹⁴C]Glc which can eventually be usedfor starch biosynthesis. The effects of specific inhibitorsof the mitochondrial adenylate translocator, i.e. atractyloside,bongkrekic acid and carboxyatractyloside were tested. Similarto the case of amyloplasts isolated from the cultured cellsof sycamore and chloroplasts isolated from spinach leaves, onlyATP and ADP-Glc uptake were shown to be partially inhibitedby carboxyatractyloside. On the other hand, neither atractylosidenor bongkrekic acid exerted a significant inhibitory effecton adenylate uptake. (Received August 8, 1992; Accepted November 26, 1992)     

Demography and social structure of one group of muriquis (Brachyteles arachnoides)

We monitored one group of muriquis, or woolly spider monkeys (Brachyteles arachnoides), over a 9-year period at Fazenda Montes Claros, Minas Gerais, Brazil. The group grew from 22 to 42 individuals due to the births of 21 surviving infants. Eight immigrations involving immature females were offset by emigrations and disappearances. The home range of the group expanded as the group size increased. The group traveled as a cohesive unit during the first 6 years of the study, but recently it has begun to show greater tendencies to fission temporarily into smaller subgroups. Six adult males from the other muriqui group at this site have simultaneously increased their associations with the main study group. These observations indicate that the group is in a state of transition which may lead, ultimately, either to its division into two smaller units or to a more fluid social structure.     

Ethanol-hypersensitive and ethanol-dependent cdc − mutants in Schizosaccharomyces pombe

Ethanol-hypersensitive strains (ets mutants), unable to grow on media containing 6% ethanol, were isolated from a sample of mutagenized Schizosaccharomyces pombe wild-type cells. Genetic analysis of these ets strains demonstrated that the ets phenotype is associated with mutations in a large set of genes, including cell division cycle (cdc) genes, largely non-overlapping with the set represented by the temperature conditional method; accordingly, we isolated some ets non-ts cdc ^? mutants, which may identify novel essential genes required for regulation of the S. pombe cell cycle. Conversely, seven well characterized ts cdc ^? mutants were tested for their ethanol sensitivity; among them, cdc1–7 and cdc13–117 exhibited a tight ets phenotype. Ethanol sensitivity was also tested in strains bearing different alleles of the cdc2 gene, and we found that some of them were ets, but others were non-ets; thus, ethanol hypersensitivity is an allele-specific phenotype. Based on the single base changes found in each particular allele of the cdc2 gene, it is shown that a single amino acid substitution in the p34^cdc2 gene product can produce this ets phenotype, and that ethanol hypersensitivity is probably due to the influence of this alcohol on the secondary and/or tertiary structure of the target protein. Ethanol-dependent (etd) mutants were also identified as mutants that can only be propagated on ethanol-containing media. This novel type of conditional phenotype also covers many unrelated genes. One of these etd mutants, etd1-1, was further characterized because of the lethal cdc ^? phenotype of the mutant cells under restrictive conditions (absence of ethanol). The isolation of extragenic suppressors of etd1-1, and the complementation cloning of a DNA fragment encompassing the etd1 ⁺ wild-type gene (or an extragenic multicopy suppressor) demonstrate that current genetic techniques may be applied to mutants isolated by using ethanol as a selective agent.     

Vertical distribution of planktonic rotifers in a karstic meromictic lake

Vertical distribution of planktonic rotifers is described in relation to temperature and oxygen in Lake La Cruz, a single-doline, closed karstic lake (121 m diameter and 25 m maximum depth) which shows iron meromixis. Samples were taken by peristaltic pumping at 10 cm depth intervals in the oxycline zone from June 1987 to September 1988. A model of rotifer vertical structure in stratified lakes is proposed. Rotifers concentrate their populations at the depths with intense gradients. As stratification develops some rotifer populations show a downward migration following the thermocline and some others show an upward migration following the oxycline. The production-respiration balance in the lake, and so the position of the oxycline with respect to the thermocline and the layer of maximum production, depends on meteorological conditions. A shift in the dominance of congeneric or related species can occur in consecutive years. In Lake La Cruz, mixing conditions and subterranean inflow in spring were much more intense in 1988 than 1987, and the distance between production and decomposition depths was smaller in 1988. Anuraeopsis miraclei, an oxycline-bound species with high abundance in 1987, was displaced by A. fissa in 1988. A. fissa, which was a metalimnetic species during early summer, reached peak densities (3 × 10⁴ ind l^–1) at the oxycline, equaling the abundance of A. miraclei the preceeding year.     

Characterization of urease from the phototrophic bacteriumRhodobacter capsulatus E1F1

Rhodobacter capsulatus E1F1 showed high cytosolic urease activity when growing on urea, purines, and purine metabolites as nitrogen source. Molecular mass ofR. capsulatus enzyme is similar to that of other bacteria and greatly differs from that of jack bean. Kinetic parameters of partially purifiedR. capsulatus enzyme resemble those described in other bacterial ureases. The activity was inhibited by metal-chelating agents and by mercurials. Urease fromR. capsulatus E1F1 was negligible in nitrogen-starved cells or in cells cultured with nitrate, ammonium, or amino acids. Moreover, ammonium inhibited both the urea uptake and the urease activity expression inR. capsulatus cells.     

Organization of the genes necessary for hydrogenase expression in Rhodobacter capsulatus. Sequence analysis and identification of two hyp regulatory mutants

A 25kbp DNA fragment from the chromosome of Rhodobacter capsulatus B10 carrying hydrogenase (hup) determinants was completely sequenced. Coding regions corresponding to 20 open reading frames were identified. The R. capsulatus hydrogenase-specific gene (hup and hyp) products bear significant structural identity to hydrogenase gene products from Escherichia coli (13), from Rhizobium liguminosarum (16), from Azotobacter vinelandii (10) and from Alcaligenes eutrophus (11). The sequential arrangement of the R. capsulatus genes is: hupR2-hupU-hypF -hupS-hupL-hupM-hupD -hupF -hupG -hupH -huoJ -hupK -hypA-hypB-hupR1-hypC -hypD -hypE -ORF19 -ORF20 , all contiguous and transcribed from the same DNA strand. The last two potential genes do not encode products that are related to identified hydrogenase-specific gene products in other species. The sequence of the 12 R. capsulatus genes underlined above is presented. The mutation site in two of the Hup^? mutants used in this study, RS13 and RCC12, was identified in the hypF gene (deletion of one G) and in the hypD qene (deletion of 54 bp), respectively. The hypF gene product shares 45% identity with the product of hydA from E. coli and the product of hypF from R. leguminosarum. Those products present at their N-terminus a Cys arrangement typical of zinc-finger proteins. The G deletion in the C-terminal region of hypF in the RS13 mutant     

Expression of the α-thionin gene from barley in tobacco confers enhanced resistance to bacterial pathogens

Thionins are cysteine-rich, 5 kDa polypeptides which are toxic to plant pathogens in vitro. Expression of the gene encoding α-thionin from barley endosperm, under the 35S promoter from cauliflower mosaic virus, conferred to transgenic tobacco enhanced resistance to the bacterial plant pathogens Pseudomonas syringae pv. tabaci 153 and P. syringae pv. syringae. The barley α-thionin gene, which has two introns, was correctly spliced in tobacco. The α-thionin in transgenic plants had the expected mobility in the gradient, when separated by high-performance liquid chromatography, reacted with monospecific antibodies and showed the expected antibiotic properties in vitro.     

Selection of synthetic proteins to modulate the human frataxin function

Frataxin is a kinetic activator of the mitochondrial supercomplex for iron-sulfur cluster assembly. Low frataxin expression or a decrease in its functionality results in Friedreich's Ataxia (FRDA). With the aim of creating new molecular tools to study this metabolic pathway, and ultimately, to explore new therapeutic strategies, we have investigated the possibility of obtaining small proteins exhibiting a high affinity for frataxin. In this study, we applied the ribosome display approach, using human frataxin as the target. We focused on Affi_224, one of the proteins that we were able to select after five rounds of selection. We have studied the interaction between both proteins and discussed some applications of this specific molecular tutor, concerning the modulation of the supercomplex activity. Affi_224 and frataxin showed a K_D value in the nanomolar range, as judged by surface plasmon resonance analysis. Most likely, it binds to the frataxin acidic ridge, as suggested by the analysis of chemical shift perturbations (nuclear magnetic resonance) and computational simulations. Affi_224 was able to increase Cys NFS1 desulfurase activation exerted by the FRDA frataxin variant G130V. Importantly, Affi_224 interacts with frataxin in a human cellular model. Our results suggest quaternary addition may be a new tool to modulate frataxin function in vivo. Nevertheless, more functional experiments under physiological conditions should be carried out to evaluate Affi_224 effectiveness in FRDA cell models.